The present invention relates to seating units having a back with back support structure adapted to change shape.
An ergonomic back construction is disclosed in Battey et al. U.S. Pat. No. 5,871,258 (hereafter the “Battey '258 patent”). The back construction in the Battey '258 patent includes a back shell positioned in front of and pivoted to an inverted U-shaped back frame at top and bottom pivots. The back shell includes a flexible lumbar section that combines with stiff thoracic and pelvic sections to cause the back to flex along a well-defined predetermined path. A biasing mechanism biases the lumbar section forwardly for optimal support to a seated user. Notably, in Battey '258, the bottom pivots are located on flanges (134) that extend forward of a front surface of the back shell, in a position where they limit overall design options and potentially interfere with laterally sliding onto the seat from a side position. It is desirable in some environments and some seating applications to eliminate interference to lateral entry onto the seat caused by the forwardly-extending flanges. Also, in Battey '258, the back frame is spaced rearwardly of and is exterior to the back shell in order to provide room for the back shell to flex. It is desirable to eliminate the need for a back frame spaced rearwardly from the back shell, since this limits design options and flexibility in regard to chair appearance. At the same time, it is desirable to maintain the ergonomic function and comfortableness of a flexible back shell construction similar to the one shown in the Battey '258 patent. Accordingly, increased design flexibility is desired for both aesthetic and functional aspects, such as to allow relocation or elimination of the top and/or bottom pivots, while maintaining a relatively simple mechanical assembly and while using environmentally-safe and environmentally-friendly (“green”) parts that can be readily disassembled and recycled.
Thus, a system having the aforementioned advantages and solving the aforementioned problems is desired.